The invention relates to a device for filtering a liquid, for instance water and more particularly drinking-water for domestic use, which filter device is provided with a filter element.
Such devices have been used for quite some time now for filtering water, and make use of for instance micro filtration and ultra filtration. Particularly micro organisms such as oocysts, cysts (Cryptosporidium, Girardia), bacteria and possibly viruses are filtered from the water by the filter element, so that the filtered water can be used as drinking-water. The first two kinds of micro organisms can be removed by micro filtration, whereas ultra filtration can also (partly) remove the other kinds of micro organisms. The filter elements that are preferably used for this purpose are based on capillary membranes (although other filter elements can be used also), and can or are exclusively provided with an inflow opening or inflow side for the liquid to be filtered and an outflow opening for the filtered liquid, or additionally be provided with one of more connections for discharging concentrate. In the latter case a flow over the membrane surface also arises, which in the classical ultra filtration is called "cross-flow" filtration. After a while such a filter element becomes dirty and cleansing it by flushing the filter element in counter direction is necessary to ensure a good working of the filter element. In the common devices the filter element needs to be removed from the device to that end. The filter element also needs to be disinfected regularly, which up until now has been done by using chemical agents added to the water going through the filter element. In the known devices the filter element cannot be used for filtering the water or the liquid during flushing the filter element and its disinfecting.